A radiological-image acquisition panel in which sensor elements that output electric charges (electric signals) corresponding to a dose of radiation, in particular, X-ray radiation that has been radiated to a subject are arranged two-dimensionally has been developed. The sensor elements are provided respectively in a plurality of pixels disposed in a two-dimensional matrix on a substrate (panel). In such a radiological-image acquisition panel, the electric charge is accumulated in a capacitive element provided in each of the pixels and a thin film transistor (TFT) element performs control to read an output corresponding the accumulated electric charge from each of the pixels.
In particular, there has been an increasing demand to reduce effects of noise that is generated, for example, in a circuit for reading an output corresponding to the accumulated electric charge. Upon such a demand, a radiological-image acquisition panel of an active pixel type in which a TFT element as an amplification element is further provided in each of the pixels and the output is amplified and transmitted to the circuit, and an image acquisition device including the panel have been actively developed.
For example, PTL 1 and NPL 1 disclose an active pixel sensor that includes a TFT for AMP (amplification of output), a TFT for READ (read of output), and a TFT for RESET (reset of the active pixel sensor). Here, the reset of the active pixel sensor refers to returning a gate voltage of the TFT for AMP to an initial electric potential that has been set, so that the drain-source current of the TFT for AMP has a predetermined value. As an active pixel sensor of the related art, there is one in which the three TFTs and the sensor element are connected as illustrated in FIG. 1. As a radiological-image acquisition panel of an active pixel type according to the related art, there is one in which active pixel sensors of FIG. 1 are disposed in a two-dimensional matrix on a substrate and which includes a Reset signal generation circuit, a Read signal generation circuit, a control circuit, and a current/voltage conversion amplifier as illustrated in FIG. 2. Note that, for convenience of description, 4×4=16 active pixel sensors in total are illustrated in FIG. 2. The Reset signal generation circuit generates and outputs signals Reset_1′ to Reset_4′ for resetting the active pixel sensors. The Read signal generation circuit generates and outputs signals Read_1′ to Read_4′ for reading output currents Iout_1′ to Iout_4′ from the active pixel sensors.
Next, FIG. 3 illustrates an example of a timing chart of an image acquisition operation by an image acquisition device including an image acquisition panel illustrated in FIG. 2. As illustrated in FIG. 3, the image acquisition device resets capacitive elements of all the active pixel sensors for each time required to read data for one two-dimensional image. Further, FIG. 4 illustrates another example of a timing chart of an image acquisition operation by the image acquisition device. As illustrated in FIG. 4, the image acquisition device suspends the read of data for a two-dimensional image and resets the active pixel sensors, and then performs the read again. Such an operation is performed on a row-by-row basis of the active pixel sensors and is performed for the active pixel sensors of all the rows in the time required to read data for one two-dimensional image.